This invention relates to a hydraulic tensioner having a piston and body or sleeve pivotally mounted to a tensioner arm and tensioner housing. More particularly, the present invention relates to a hydraulic tensioner in which a first end of the tensioner is pinned or pivotally mounted to a tensioner arm while the second end of the tensioner body, located opposite the first end, is pivotally mounted to an engine block or other mounting block.
Hydraulic tensioners are typically used as a control device for a chain drive system in an automobile timing system. The tension in the chain can vary greatly due to the wide variation in the temperature and the linear thermal expansion among the various parts of the engine. Moreover, wear to the chain components during prolonged use can produce a decrease in the tension of the chain.
A hydraulic tensioner is conventionally used to take up the slack in the chain that connects the crankshaft to the camshaft in an engine timing system. The typical hydraulic tensioner includes a housing with a bore, a hollow piston slidably received in the bore and a fluid chamber defined by the piston and the bore. The piston is biased in a protruding direction from the bore by a spring. A check valve is also included in the hydraulic tensioner to permit fluid flow from a source of pressurized fluid into the fluid chamber, while preventing back flow in the reverse direction. The piston is typically pressed against a tensioner arm or other device to provide tension to the chain. The force of the chain against the piston in an inward direction is balanced by the resistance force of the fluid and force of the spring in an outward direction.
In one embodiment, the present invention provides a hydraulic tensioner that has a piston pivotally connected to a tensioner arm at one end and a spherically-shaped sleeve or body at the other end. The spherically-shaped body incorporates an oil feed from a ball and socket inlet port. The oil feed inlet port is mounted to an engine head or block.
The present invention is directed to a pivoting hydraulic tensioner with an integral mounting feature and oil feed. In one embodiment, a hydraulic tensioner includes a body formed of a generally cylindrical hollow sleeve with a spherically-shaped lower end. The lower end includes a fluid passage to permit fluid flow into the hollow sleeve. A hollow piston having a closed end and an open end is slidably received within the hollow sleeve. The open end of the piston is positioned in the sleeve to form a fluid chamber with the sleeve.
A spring is also positioned within the hollow piston to bias the piston in a protruding direction from the sleeve. A check valve is also positioned within the fluid passage between the chamber and a source of pressurized fluid to permit fluid flow into the fluid chamber while blocking flow in the reverse direction. As the chain slackens, the force of the spring moves the piston away from the base of the sleeve and fluid is caused to flow into the fluid chamber. As the chain tightens, the force of the chain inward against the piston is balanced by the force of the spring and the resistance force of the fluid chamber.
The piston is pivotally connected at the closed end to permit attachment to a tensioner arm. A pivot pin disposed with the pivot connection permits pivotal mounting of the tensioner arm. The spherically-shaped end of the sleeve is also received or held in a spherically-shaped body, which is mounted to an engine block. The spherically-shaped body provides a fluid passage from the source of pressurized fluid to the fluid passage in the sleeve.
In another embodiment, the spherically-shaped body is located within a tensioner housing. In yet another embodiment, the sleeve is pivotally connected to the tensioner arm and the piston has a spherically-shaped end that is held in the mounting block. A retaining ring is placed along the outside of the piston. The retaining ring fits into a groove machined into the sleeve when the piston reaches its uppermost point, that is, the point furthest out of the sleeve, and prevents further outward movement.
Fluid is supplied by a reservoir and flows through a passageway to the check valve and into the pressurized chamber. To produce a pressure differential, a compression spring is commonly used to provide a bias force on the tensioner piston. This produces a vacuum in the chamber as the piston is urged away from the check valve and permits flow through the valve into the chamber. As the chain slackens and tightens, the piston protrudes and withdraws in response to the vibration of the chain. The outward force of the spring and fluid on the piston balances the inward force of the chain on the piston.
In yet another embodiment, the tensioner has a mounting hole formed in a bottom end of the sleeve of the tensioner opposite the open end of the sleeve. A mounting pin is inserted into the mounting hole of the tensioner. The mounting pin allows pivoting of the tensioner housing around the central axis of the pin. In other words, the mounting pin limits the rotational direction of the tensioner to a plane perpendicular to the longitudinal axis of the pin. The mounting pin may be an integral part of a mounting plate fastened to the engine or may be part of a separate mounting pin assembly fastened to the engine. The mounting pin may have retaining clips or other fastening means to keep the tensioner body mounted upon the pin. In addition, the mounting pin may have O-rings positioned around the shaft of the pin to provide a fluid seal between the pin and the tensioner.
In all embodiments of the present invention, the end of the tensioner in contact with the tensioner arm is allowed to pivot relative to the tensioner arm and the other end of the tensioner in contact with a mounting block or mounting pin attached to the engine is also allowed to pivot. In other words, the first end, which is the end of the tensioner which contacts the tensioner arm, may be either the piston or sleeve end of the tensioner. The second end, which is the end of the tensioner mounted to the engine block, may be either the piston end or the sleeve end of the tensioner.